Metal alloy powders heretofore have been produced by gas or water atomization of molten ingots of the alloy. It has not been generally practical to produce the metal alloy powders directly from the individual metal powders because of the difficulty in obtaining uniformity of distribution of the metals. It is difficult to obtain certain powders containing readily oxidizable metals such as aluminum because of the tendency of those metals to form the respective oxides which are stable during processing.
U.S. Pat. No. 3,909,241 relates to free flowing powders which are produced by feeding agglomerates through a high temperature plasma reactor to cause at least partial melting of the particles and collecting the particles in a cooling chamber containing a protective gaseous atmosphere where the particles are solidified. In this patent the powders are used for plasma coating and the agglomerated raw materials are produced from slurries of metal powders and binders. Both U.S. Pat. Nos. 3,663,667 and 3,909,241 are assigned to the same assignee as the present invention.
In U.S. Pat. No. 4,613,371, issued Sept. 23, 1986, also assigned to the assignee of this invention, there is disclosed a process for making ultra-fine powder by directing a stream of molten droplets at a repellent surface whereby the droplets are broken up and repelled and thereafter solidified as described therein. While there is a tendency for spherical particles to be formed after rebounding, it is stated that the molten portion may form elliptical shaped or elongated particles with rounded ends.
U.S. Pat. Nos. 3,663,667; 3,909,241; 3,974,245; 4,502,885 and 4,508,788, all relate to formation of free flowing powders via the production of agglomerates and feeding agglomerates through a high temperature plasma reactor to cause at least partial melting of the particles. Resulting powders are spherical and free flowing. These patents relate to the use of metal agglomerates and not to powder particles which necessarily have a uniform distribution of constituents throughout the agglomerate.
It is believed therefore that a relatively simple process which enables finely divided iron group metal or iron group based alloy powders containing such readily oxidizable metals to be produced from sources of the individual metals would be an advancement in the art.